The present invention refers to the electronic locks for controlling access to enclosed areas to a limited number of persons.
Electronic locking systems are widely used for controlling access to enclosed areas to a limited number of persons.
Conventional mechanical locks do not resolve the problem of the loss of keys and the deactivation of the same in a simple and versatile manner.
There exist on the market numerous electronic locking systems which use different devices (cards or electronic keys, etc.), in which the device lost by a user can be deactivated in a simple manner, issuing a new device to that user. When the lock reads that device, it automatically invalidates the previous device and accepts the new device as valid.
Tor Somes"" U.S. Pat. No. 4,519,228 (xe2x80x9cElectronic recodeable lockxe2x80x9d) describes an electronic lock which uses a perforated card with a magnetic strip. A recoding command is stored in the magnetic strip and indicates that the access code for the lock should be changed to the code of the perforated card.
What is inconvenient about this solution is the high cost of the mixed card (perforated and magnetic) as compared to solutions which use a standard magnetic card.
Crafton""s U.S. Pat. No. 3,906,447 (xe2x80x9cSecurity system for lock and key protected secure areasxe2x80x9d) describes a security system for areas controlled by electronic locks in which each user has a device (perforated or magnetic card, etc.). In order to access a restricted area, the lock must read the user""s device. Each lock and each user""s device stores a code. When the code of the device read by the lock matches a code stored in its memory, access to the restricted area is permitted by the lock. In each user""s device an order code is also stored, which represents a time. This time coincides with the moment at which each device is issued. The lock compares the device""s order code with the time stored in the lock at the moment the user""s device is read. If the order code of the device is higher than the time store in the lock at the moment the device is read, the lock stores the device""s code as a new code, invalidating the previous code of the device. The system described in this patent is composed of a unit dedicated to coding the user""s devices. This unit has the means to store a counter which represents a time, and the means to advance this counter at regular intervals. The lock has means to store a counter which represents a time in a similar manner. The user""s device also stores a code which represents the time at which its access to the door expires. The lock automatically invalidates the device""s code once the time stored by the lock coincides with the expiration time of the device.
The fundamental disadvantage of this system is that it is necessary to maintain a permanent synchronization between the internal time of the locks and the time of the issuers of the devices. If for any reason these two times are not synchronized, the system stops working or functions incorrectly.
Another disadvantage is that it is only possible to store one device code per lock, so it is not possible for two users with different devices to access the door.
Another inconvenient feature of the invention is that each lock must have additional space in its memory to store the expiration time of the device in addition to the device code.
Juan Imedio""s ES Patent No. 532,333 (xe2x80x9cNew programmable electronic lockxe2x80x9d) describes an electronic lock which consists of a card which stores a code which is composed of a card code and a sequential code. When the card code read by a lock coincides with the code stored by the lock, access to the area restricted by the lock is permitted. If the card code is higher than the code stored in the lock by one unit, the previous code is invalidated and the new card code is stored.
Juan Imedio""s ES Patent No. 92-02,223 (xe2x80x9cNew programmable electronic lockxe2x80x9d) describes an electronic lock which uses cards and is based on the previous Patent No. 532,333 by the same person. The fundamental difference with the previous patent is that if the card code is higher than the code stored in the lock by one or more units, the previous code is invalidated and the new card code is stored.
The fundamental inconvenience of this type of system is that the sequential code of the locks only advances if the new users insert their devices in the locks. Frequently the advancement of the sequential codes of the locks is only permitted if the difference between the card code and the sequential code stored in the lock is not greater than a maximum value. If this is not the case, access to the lock is not permitted. For this reason, if new devices are issued and these do not access a lock (for example a low traffic access such as an emergency exit), the lock does not advance its stored sequential codes and loses synchronization with the codes of the newly issued devices, making it necessary to resynchronize the lock with an external means in the case in which the new devices are issued with a code which is higher than the maximum value stored in the lock.
Another inconvenience of this system is the complexity of creating user devices in advance. At times it is necessary to issue devices which will be valid at a time later than the date of issue of the device. The method used in these cases consists in assigning a sequential code which is several units higher rather than assigning the following sequential code. This method is not satisfactory given that it is not possible to know in advance the number of devices which will be issued before the device assigned in advance is read by the lock. In the case in which the number of devices issued is greater than the number of devices anticipated before the device issued in advance, the latter will not be valid as its sequential code will not lower than that stored in the lock at that time, and it will be necessary to resynchronize the lock with an external means.
Another inconvenience of this system is the complexity of issuing user devices from locations which are distant from each other. Given that it is necessary to know at all times the sequential code stored in the locks, at the time of issuing a new device, it becomes necessary to have a means by which to extract said code or maintain a synchronized copy of the same at each location where devices are issued. This implies the necessity of exchanging information frequently through some system of communication of data, which implies a higher cost and complexity.
The subject of the present invention is a security system which takes as a reference Crafton""s U.S. Pat. No. 3,906,447 (xe2x80x9cSecurity system for lock and key protected secured areasxe2x80x9d).
This system permits the control of access of the users of an installation to certain areas, and is composed of the following elements:
A physical device capable of storing a user code and an order code which represents the time at which said device is issued and optionally capable of storing zone codes which represent the zones accessible by said device and a physical device in which the information contained is stored in a coded form according to a coding algorithm and a secret code which is different for each installation,
An electromechanical locking system which controls access to the zones,
Issuers for the devices capable of storing information in the devices of the Users, information which is stored in a coded form according to a coding algorithm and a secret code which is different for each installation,
Programmers capable of transferring information to the electronic circuits of the doors,
A computer which manages the entire installation and is responsible for sending information to the users"" device issuers and to the programmers of the door modules.
The electromechanical locking system is constituted by the following elements:
An electronic circuit which generates an electronic signal to release the electromechanical control system,
A reader module or modules capable of reading the information contained in the users"" devices,
An electromechanical control system governed by an electrical signal capable of controlling access to an area.
The principal advantages of the system described are:
It is not necessary to maintain synchronous functioning between the time counter of the lock and that of the device issuer.
The need to have some kind of communication between the remotely located device issuers is eliminated. It is only necessary that their time counters be synchronized. These time counters can be synchronized with the normal hourly time, which is a simple and universal form of synchronization.
The electronic circuits cannot lose synchronization with the devices issued as a new device accesses a permitted area whenever it issues a later order code.